The point I'm making is that the script changes the value depending on what you have equipped, and with the mod disabled the value STILL changes depending on what you have equipped, as if the mod was enabled.
So let's see if I understand you. Your point is that if you enable the mod and save the game while having both hands equiped so the speed buff is reverted, then you exit the game, disable the mod, reopen the game and load the savegame then player.getav weaponspeedmult is still returning 1.15?
It's that's the case I would try setting it to 0 via console, saving and loading to see if it's still changing...but it should not if the mod is disabled...
EDIT: Because you created a new script, right? I mean you didn't reuse a vanilla one, did you?